The CPU will show a slow blinking FRCE or STOP LED (indicating it requests a reset).
Insert the card into a Field PG or a USB Prommer. In Step 7, go to File > S7 Memory Card > Delete . This performs a "logical" format that clears user data without destroying the system partition.
: Unlike Windows formatting, which overwrites the proprietary Siemens header, this tool attempts to reconstruct the specific internal structure required by SIMATIC devices. siemens mmc card format tool
How to Format a Siemens MMC Card Correctly Doing so will erase the special internal file system and permanently ruin the card. Siemens PLCs (like the S7-300 and S7-400) use a unique data structure that normal computers cannot read or create.
Typical use cases
To safely format, erase, or recover these cards, you must use specific Siemens MMC card format tools and procedures. The Danger of Standard Windows Formatting
For engineers and technicians working with Siemens SIMATIC S7-300 and S7-400 PLCs, the Micro Memory Card (MMC) is a critical component. It stores the user program, hardware configuration, and data blocks. However, these cards can become corrupted, filled with unwanted data, or simply need a fresh start. The CPU will show a slow blinking FRCE
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Download a verified raw image file corresponding to your exact Siemens MMC part number from a trusted automation forum. This performs a "logical" format that clears user
